The present invention relates to new constructions of bushing wells for electrical apparatus enclosures, and particularly, constructions which provide for feed through capability from one separable terminator to a second separable terminator. The bushing well constructions of the present invention reduce the space requirements for the bushing well and the separable terminator and reduce cantilever loading of the bushing well.
Bushing wells are well known in the art having their primary application in the field of electrical power distribution systems. In such applications, several pieces of electrical apparatus may be connected in parallel to a single feeder line.
Prior to the development of bushing wells, connections to enclosed electrical apparatus, such as transformers, were commonly accomplished by providing an insulated stud passing through the enclosure to which a spade terminal was secured. Incoming and outgoing cables were then bolted directly to the exposed spade terminals which may then have been wrapped with an insulating material. Making and breaking these electrical connections is extremely costly and time consuming. This "live front" design is unsatisfactory from a safety standpoint also as lineman may accidently come into contact with the exposed line connector. As the useful life of such electrical equipment is relatively long, many of these "live front" designs are still in use. Accordingly, it is desirable to adapt these "live front" units to the "dead front" design using bushing wells. Often, however, space restrictions prohibit the addition of a second opening for a second bushing well. This is particularly true for three phase transformers. Thus, it is desirable to employ a feed through type bushing well. Feed through capability had previously been provided by incorporating two separate bushing wells on the face of the enclosure with a jumper strap electrically connecting them interiorly of the enclosure. As is apparent, such an arrangement is costly to manufacture, both in labor and materials. Further, as two separate openings in the enclosure are required, the possibility of insulating fluid leakage is greatly increased.
More recently, bushing wells have developed which provide feed through capability integral to the bushing well. Such a bushing well is disclosed in the U.S. Pat. to Fisher, No. 3,909,509, issued May 1, 1975, and assigned to the same assignee as the present application.
In use, the electrical connection to bushing wells is normally made by grasping a separable connector with a hot stick and inserting the connector into the bushing well assembly. As a bushing well providing feed through capability must necessarily have connector portions offset from the portion passing through the enclosure wall, such operation of the connector produces a cantilever stress on the bushing well assembly itself. These forces may result in a cracking of the bushing well itself or cause sufficient distortion of the enclosure wall to allow insulating fluid to escape.
The present invention provides a bushing well having feed through capability which overcomes these problems.
The present invention provides lateral supporting legs which engage the enclosure thus substantially relieving the cantilever loading resulting during operation of the connector. Also, as the present invention has integral feed through capability and requires only slightly more space than prior "live front" terminals, it may easily be installed in place thereof.
Further, the present invention provides a means to removably clamp the bushing well to the enclosure thus allowing field replacement without the necessity of replacing the equipment.
Further, means are also provided to limit the clamping pressure exerted on the gasket and also to retain the gasket in position, thus ensuring the most advantageous sealing relationship may be easily obtained even underadverse field conditions and by less highly trained personnel.
A second embodiment of the present invention has an elongated conductor portion extending interiorly of the enclosure a substantially greater distance than that of the interiorly extending conductor portion of the first embodiment. This elongated shank is particularly suited for application in which the bushing well is mounted on the top of the enclosure as its extended shank allows the lead connections to be made below the level of the insulating fluid.
These and other advantages and features of the invention will become apparent from the detailed description of the preferred embodiment below.